1. Field of the Invention
This invention relates to hall effect generators and more particularly to hall effect generators made up of multiple orthogonal pairs of hall effect plates with their output contacts connected in parallel.
2. Description of the Prior Art
The application of the hall effect in semiconductors to contactless mechanically-actuated switching has been known for many years. Until recently, however, hall effect devices had not come into widespread use because of their high cost and low sensitivity. It has been felt that to achieve sufficient output voltage with low offset, it was necessary to employ high mobility materials such as InAs-InP alloys for generators, but inexpensive production methods for these materials and devices have not been developed.
Progress in silicon technology has now made it possible to overcome the low mobility and poor sensitivity of silicon by fabricating circuits in which hall effect generators, preamplifiers, signal conditioning circuits and trigger circuits are integrated on the same semiconductor chip.
Although sensitivity and temperature effects are problem areas, the major problem in silicon hall effect generators is offset voltage; i.e., the residual output voltage when no magnetic field is applied. This voltage arises when the required symmetry of the generator is not preserved, and can result from various influences, such as mask and alignment errors, doping inhomogeneities, non-uniform diffusion at contacts or at the periphery of the generator, shear stresses, extended defects, etc. The combined effect of these influences leads to offset voltages which vary unpredictably from chip to chip over a slice and which may be comparable to or exceed the anticipated hall voltage.
The current approach to this problem involves individual functional probling and possibly trimming of each chip on a slice, and this significantly increases slice cost.
The present invention, by positioning a pair of hall effect plates in orthogonal relationship to each other and using a plurality of such orthogonal pairs with the hall voltage contacts connected in parallel, reduces the cost of fabrication because absolute accuracy of alignment and masks, as well as total freedom from stress error voltages is not required.